Human development can result in chemicals, waste, and/or agricultural runoff being introduced into the ecosystem. Increases in population may lead to over-harvesting of marine resources, landscape alterations that alter the ecosystem, and the introduction of living and non-living contaminants into the ecosystem (Mallin, M. A, et al. 2000, Marine Pollution Bulletin, 41:56-75). Additionally, as the threat of bioterrorist activities has become evident in recent years, concern about the vulnerability of ecosystems such as municipal water supplies to deliberate contamination has grown.
For example, water and/or other ecosystems may be contaminated with heavy metals, such as mercury. Such contamination may enter water supplies through natural deposit erosion, factory and refinery discharges, landfill/cropland runoffs, and coal power plant emissions. Most of the mercury in lakes and sediments exists in the more reactive inorganic mercuric form Hg(II), which can be effectively transported across microbial membranes and subsequently converted to organic mercury compounds, or methyl mercury (MeHg) (Morel et al., 1998, Ann. Rev. Ecol. Syst. 29:543-66.). Although the conversion of inorganic mercury to organic mercury may occur under aerobic conditions, it is predominantly due to dissimilatory sulfate or iron reducing bacteria under anoxic conditions (Kerin et al., 2006, Appl. Environ. Microbiol. 72:7912-7921). MeHg is a highly toxic compound and may constitute up to 20% or more of the total mercury concentration in sediments (Osborne, et al., 1997, FEMS Microbiol. Rev. 19:239-262; Nascimento and Chartone-Souza, 2003, Genet. Mol. Res., 2:92-101). Since mercury can accumulate in living tissues, its concentration tends to be greater at higher trophic levels of the natural food chain. Consequently, ongoing, low-level consumption of mercury-laden food poses a chronic health risk to humans. Other contaminants may be equally as problematic.
Reservoirs, recreational lakes, and coastal areas can be difficult to secure against accidental or intentional contamination. Further, the contamination of a water source has the propensity to impact a relatively large population, and water filtration systems may not sufficiently alleviate the threat. Also troubling is the lack of a real-time test to detect the agents that are most likely to contaminate water supplies. The turnaround times for culturing microbes and/or obtaining chemical test results is slow enough that consumption of contaminated water may occur before the test results are known. Also, the expense involved in frequent monitoring of the water supply with currently available laboratory tests can be prohibitive.
As yet, there has not been a large-scale, deliberate contamination of a municipal water source. However, sporadic and relatively confined natural contaminations have demonstrated the importance in being able to monitor the water supply. The number of outbreaks attributable to contaminated drinking water supplies more than doubled in 1999-2000 over the previous two-year period, with contamination of well water also on the rise. In addition, recreational water sources have also reported significant increases in contamination (Bowman, 2002, Outbreaks of waterborne illnesses on the rise in US, Scripps-Howard News Service, Nov. 23, 2002). These incidents of water contamination were exacerbated by the difficulty in pinpointing the cause of the outbreak and subsequent misdiagnosis of the symptoms, illustrating the importance of “early warning” diagnostics of water supplies.
A number of microbial genome sequencing projects have been initiated to characterize pathogenic organisms. Although identification and characterization of genomic sequence data for individual pathogens may provide for the identification of specific microbes, such targeted testing fails to provide a comprehensive, economically feasible system for monitoring ecosystems of interest, such as municipal water supplies. The accuracy of a molecular diagnostic test for a microbe may be compromised where the pathogenic agent is endemic, or possesses substantial genetic similarity to non-pathogenic organisms (Leff et al., 1995, Appl. Environ. Microbiol., 61:1634-1636; Xiao et al, 1999, Appl Environ. Microbiol., 65:3386-3391). Also, although some putative contaminants of water have been identified, anticipating all possible contaminants is not feasible, and thus, specific tests are inherently limited.
Thus, there is a need for devices and methods that enable real-time monitoring of water supplies and other ecosystems of interest. The monitoring system should allow for detection of known, as well as unknown, contaminants. The monitoring system should be available in a format that is accessible for routine monitoring, as well as for rapid testing in response to a specific event.